Abstract:
An international team of physicists has entangled three diamond nuclei for the first time. The development promotes solid-state systems to a rank of quantum systems including ions and photons that have achieved entanglement for more than two particles.

Entanglement lies at the heart of fields such as quantum computation and quantum teleportation. At its most basic level, if two particles are entangled a measurement of the state of one reveals something about the state of the other, regardless of the distance separating them.

But entanglement is difficult to achieve. It requires quantum states to be manipulated while preventing them from interacting with their environment, which tends to degrade the quantum system into a classical state. Physicists have had some successes, having entangled up to eight calcium ions and up to five photons. So far, however, solid state systems have proved trickier.

Now, a team led by Jöerg Wrachtrup of the University of Stuttgart, Germany, has demonstrated that two or three diamond nuclei can be entangled (Science 320 1326). "If we compare the quality of entanglement in our experiments with those [of ions and photons], our results compare favourably," says Wrachtrup. His team includes researchers from the University of Tsukuba, the National Institute of Advanced Industrial Science and Technology, and the Nanotechnology Research Institute, Japan, and Texas A&M University, US.